Optical Material Polymerization Viscosity Control
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Solution Overview
Problem
The production of optical materials, particularly plastic lenses, faces challenges with high viscosity during prepolymerization reactions, leading to difficulties in filtration and mold injection, poor mold release characteristics, and the generation of striae, especially in lenses with high minus power. Existing methods require high reaction temperatures, which increase viscosity and reduce productivity.
Innovation Solution
A polymerizable composition comprising sulfur, a compound with two intramolecular episulfide groups, and a compound with one or more SH groups, processed using a hindered amine as a prepolymerization catalyst, is subjected to a prepolymerization reaction at a temperature near room temperature, reducing viscosity and improving mold release characteristics while minimizing striae formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the content of inorganic compound having sulfur atom and/or selenium atom is increased to achieve high refractive index, then the refractive index is improved, but the viscosity of polymerizable composition becomes too high making filtration and mold injection difficult
Solution Approach 1:
The patent applies preliminary action by conducting a prepolymerization reaction before the main polymerization process. The inorganic compound (sulfur or selenium) is pre-reacted with the polyepisulfide compound at 50-70°C for 1-24 hours to form a preliminary reaction solution with controlled viscosity. This preliminary reaction creates intermediate products that can be easily filtered and injected, while still achieving the desired high refractive index in the final optical material.
Solution Approach 2:
The patent utilizes parameter changes by controlling the temperature and time of the prepolymerization reaction. By maintaining the reaction temperature at 50-70°C and limiting the reaction time to 1-24 hours, the viscosity of the composition is kept at manageable levels during the preliminary reaction stage, enabling easy filtration and injection operations while still incorporating sufficient inorganic compound content for high refractive index.
2Speed
If the reaction temperature is increased to speed up the prepolymerization reaction, then the reaction speed is improved, but the viscosity of the composition increases making injection operations difficult
Solution Approach 1:
The patent optimizes the reaction temperature parameter to 50-70°C, which is sufficiently high to achieve acceptable reaction speeds but not so high as to cause excessive viscosity increase. This temperature range balances reaction kinetics with operational feasibility, allowing the prepolymerization to proceed at a practical rate while keeping the composition fluid enough for filtration and injection operations.
Solution Approach 2:
The patent implements a preliminary reaction step at controlled temperature (50-70°C) that prepares the composition for subsequent injection without requiring excessive heat. This preliminary action at moderate temperature avoids the viscosity problems that would occur with high-temperature reactions, while still achieving sufficient reaction progress to enable easy handling and injection.
3Reliability
If the prepolymerization reaction is performed excessively or at too high temperature, then the reaction completeness is improved, but the viscosity after 3 hours significantly increases making injection operations difficult
Solution Approach 1:
The patent applies preliminary action by conducting a controlled prepolymerization reaction that achieves sufficient reaction completeness without over-reacting. The reaction is performed at 50-70°C for 1-24 hours, which is enough to create the necessary intermediate structures for good mold release and optical properties, but limited enough to prevent excessive viscosity buildup that would hinder injection operations.
Solution Approach 2:
The patent uses partial action by not allowing the prepolymerization reaction to go to complete exhaustion. Instead, the reaction is controlled to reach an optimal point where sufficient conversion has occurred to achieve good mold release characteristics and optical material properties, but before the viscosity becomes prohibitively high for injection operations.
4Productivity
If the reaction temperature is set high to reduce cooling time, then the productivity is improved, but the viscosity increases and makes filtration and injection difficult
Solution Approach 1:
The patent optimizes the reaction temperature parameter to 50-70°C, which provides a balanced approach: high enough to maintain acceptable reaction rates and reduce cooling requirements, but not so high as to cause excessive viscosity increase that would complicate filtration and injection operations. This temperature optimization achieves productivity improvement without sacrificing operational ease.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for easier control of the prepolymerization reaction endpoint, reduces cooling time, enhances filtration and injection operations, and improves the productivity of optical materials with improved mold release characteristics and reduced striae, especially in high minus power lenses.
Implementation Method 1
using 0.001 to 10 parts by mass (the upper limit is preferably 5 parts by mass or less, and more preferably 3 parts by mass or less) of the below-described compound (d) as a prepolymerization catalyst
Implementation Method 2
a polymerizable composition for optical materials, in which an inorganic compound having a sulfur atom and/or a selenium atom is blended with a polyepisulfide compound
Data Source
AI summary
By using a method for producing a composition for an optical material using (a) sulfur, (b) a compound having two intramolecular episulfide groups, (c) a compound having one or more (preferably two) SH groups, and (d) an amine compound having a specific structure, in which compound (a) and compound (c) are pre-polymerized in the presence of compound (b) using compound (d) as the pre-polymerization catalyst, the present invention provides a polymerizable composition for an optical material in which the viscosity elevation speed during pre-polymerization is slow and the reaction temperature is approximately room temperature, and that has a low viscosity and shows little increase in viscosity. By means of another embodiment of the present invention, it is possible to produce an optical material that has excellent mold release characteristics but has substantially no striae by polymerizing (a) sulfur, (b) a compound having two intramolecular episulfide groups, and (c) a compound having one or more SH groups in the presence of (d) a hindered amine catalyst having a specific structure.